1. Field of the Invention
The present invention relates to a communication unit, which implements an authentication process and to a method for controlling the communication unit.
2. Description of the Related Art
There is a wireless USB system to realize USB protocols with wireless communication. In the wireless USB system, an authentication process between a communication host and a communication device is required before starting communication. There are numeric and cable associations within the authentication process.
In the numeric association authentication process, a communication device is wirelessly connected to a host and keys are exchanged between them. Then, if a numeric number displayed in the host matches a numeric number displayed in the communication device as a result of the key exchange, the authentication process is complete after each button for verifying match of the keys is pushed at both the host and the communication device. If the numeric number displayed does not match, or if only one numeric number is displayed in the host or the communication device, the authentication process does not complete successfully.
Now consider a case where a user having a digital camera uses a printer to print an image stored in the digital camera. The printer has a wireless USB host communication function while the digital camera has a wireless USB device communication function. The host and devices for wireless USB communication also support the WiMedia specification. The WiMedia specification is a specification for the communication layer below the Wireless USB specification.
FIG. 1 shows operation sequences for the case of having a plurality of printers. It is assumed that a user 100 would like to perform an authentication process in order to connect the digital camera to the printer B which is nearest to the digital camera.
Step 400: It is assumed that another user 303 has already pushed the button of the printer A and the button of his digital camera for starting the authentication process.
Step 401: Then, the user 100 pushes the button of the printer B for starting the authentication process.
Step 402: The user pushes the button of the digital camera 101 for starting the authentication process.
Step 403: Because the button for stating authentication is already pushed, MMC information of the printer A will indicate an available state of receiving authentication (ConnectAvailability=ALL). In this case, it is assumed that the digital camera 101 discovers the information stored in MMC of the printer A, as a matter of course.
Step 404: Therefore, the digital camera is then connected to the printer A. Because it is not possible to obtain device information prior to authentication in the Wireless USB specification, the digital camera will be connected to the device which it discovers first.
Step 405: The digital camera 101 receives a connection acknowledgement via a Connect ACK of the MMC information transmitted from the printer A.
Step 406: The digital camera 101 and printer A exchange keys with each other.
Step 407: The numeric characters are displayed on a display of the printer A.
Step 408: The numeric characters are displayed on a display of the digital camera.
However, the user may recognize that the authentication has failed because the numeric characters of the authentication are not displayed on the display of the printer B. Thus, the printer B by which the user 100 would like to print the image, cannot be connected to the digital camera because the key was exchanged for the printer A, which was discovered first. Therefore, the user must repeat the authentication process from the beginning. However, even if the authentication process is applied again, successful authentication depends on the operational status of other printers and is not guaranteed to succeed for the printer B near the digital camera thus becoming a source of user frustration.
Japanese Patent Laid-Open No. 2004-015654 describes a communication unit that is connected to a target communication unit based on information of from other communication units regarding received power levels, which communication units collect by transmitting their received power signal level to each other. However, the RF receiving level is variable, and accurate measurement of range using the RF receiving level is not possible.
In the past, communication units sometimes have difficulty in rapidly authenticating other communication units with which a user wishes to communicate, among a plurality of other communication units.
The present invention provides a wireless communication unit for rapidly authenticating with other wireless communication units with which a user wishes to connect.